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+1 Also depends on the track temp and how hard and long you run them in a session. It was cool in Charlotte and I was only able to get the tire pressures to rise around 6 pounds on all but one session in which I got a lot of clear track to run on.
They'll go hotter. Use the hot pressures to get the car handling then let them cool overnight and you'll have a new set of starting pressures. I would advise using nitrogen or at least dehumidified air because the any moisture in the tire can cause the pressures to vary widely including "spiking". Don't be afraid to run different pressures at all 4 corners to get the car to work.
At that point you'll need some expensive gauges and / or a guy like me to take you further.
Again, and this is vital, you need to use either dehumidified air or nitrogen, at the upper levels moisture in the tire over 20% will cause the air pressure to spike, this could be adding to the high pressures, if this is happening in one or two tires or not the other you will never get the setup right.